Process for refining nitrogen trifluoride gas using alkali earth metal exchanged and impregnated zeolite
Disclosed herein are a process for the refinement of nitrogen trifluoride gas and an adsorbent therefor. A nitrogen trifluoride (NF3) gas including carbon tetrafluoride (CF4) as an impurity is permeated into a bed of zeolite 3A, 4A or 5A which undergoes ion exchange and impregnation with alkali earth metal and is thermally treated at 150 to 600° C. for 0.5 to 100 hours so as to be able to selectively adsorb nitrogen trifluoride onto the bed, followed by the desorption of the nitrogen trifluoride therefrom.
1. A process for refining nitrogen trifluoride gas, comprising:
introducing a gas mixture of nitrogen trifluoride (NF3) and carbon tetrafluoride (CF4) into a bed of zeolite 3A, 4A or 5A to selectively adsorb nitrogen trifluoride onto the bed, with the carbon tetrafluoride passing through the bed, said zeolite 3A, 4A or 5A being ion-exchanged and impregnated with alkali earth metal; and
recovering the nitrogen trifluoride from the bed.
2. The process as defined in claim 1 , wherein the zeolite contains the ion-exchanged alkali earth metal in an amount of 20 to 95% by weight based on the total weight of the metal within the zeolite and the impregnated alkali earth metal in an amount of 0.1 to 5% by weight based on the total weight of the zeolite.
3. The process as defined in claim 1 , wherein the alkali earth metal is magnesium (Mg).
4. The process as defined in claim 1 , wherein the alkali earth metal is calcium (Ca).
5. The process as defined in claim 1 , wherein the alkali earth metal is strontium (Sr).
6. The process as defined in 1, wherein the alkali earth metal is barium (Ba).
7. The process as defined in claim 1 , wherein the gas mixture of NF3 and CF4 is introduced into the bed at a temperature of −100 to 50.degree.C.
8. The process as defined in claim 1 , wherein the gas mixture of NF3 and CF4 is introduced in combination with an inert gas into the bed, said inert gas amounting to 20 to 80 vol % based on the total volume of NF3, CF4 and the inert gas introduced.
9. The process as defined in claim 8 , wherein the inert gas is selected from the group consisting of argon, helium and nitrogen.
10. The process as defined in claim 1 , wherein the introducing step of adsorbing nitrogen trifluoride (NF3) onto the zeolite 3A, 4A or 5A ion-exchanged and impregnated with the alkali earth metal and recovering step of nitrogen trifluoride from the zeolite are sequentially repeated two or more times.